In 1998 the Department of Transportation (DOT) spent 2.9 billion dollars on upgrading and maintaining the interstate system. The DOT estimated that 4.1 billion would be required to maintain the system in 1999. Likewise individual states spend millions of dollars each year building new roads and keeping state roads in good repair. A good road must have a solid base. A solid base is created from screened gravel which is graded in size to intermesh and pack securely. To obtain suitable road base material, rock and gravel removed from the earth must be screened to a uniform size. Screening this rock and gravel is done using a crude grizzly. The grizzlies used in this process are typically a square frame supporting a plurality of evenly spaced parallel bars which form a grate. The face of the grate is positioned at a slight angle from horizontal so that as rocks and gravel are poured onto it, small gravel falls through the bars and is separated from larger rocks which slide off the inclined face of the grizzly and are collected for further processing by crushing.
Grizzlies are used in a number of industries to size products for use and sale. Apples, as well as many other fruits and vegetables, are graded by size. Fish are sized at hatcheries, separated and graded for sale. Distinguishing several grades requires using several grizzlies having a variety of grate sizes. Alternatively, grizzlies can be used which have adjustable bars that can be set to provide several grate sizes. Grate size is determined by the width of the spaces between the parallel bars. Adjustable grizzlies have been described which have complicated lever systems to move bars apart or together to adjust the grate size (U.S. Pat. No. 1,109,866). Telescoping bars which are thicker at the base and become progressively thinner when placed side by side provide a variety of grate sizes along a single path (U.S. Pat. No. 1,491,802). Adjustable grates have been described that allow the removal of every other bar to provide a larger grate size (U.S. Pat. No. 47,041). Sleeves to be slipped over the grate bars have been described which reduce the size of the spaces between the bars forming a smaller grate size (U.S. Pat. No. 3,833,119). The space between bars is varied by changing the distance between an upper and lower set of bars in U.S. Pat. No. 555,973. The aforementioned adjustable grizzlies however do not provide the flexibility of offering a variety of grate sizes while being strong enough to withstand the rigors of sorting gravel and rock. Thus there is a continued need for an adjustable grizzly that is convenient and durable.
All patents, patent applications, provisional patent applications and publications referred to or cited herein, or from which a claim for benefit of priority has been made, are incorporated by reference in their entirety to the extent they are not inconsistent with the explicit teachings of the specification.
The subject invention involves an adjustable grizzly. The grizzly can be adjusted to provide a variety of grate sizes. A frame supports a plurality of parallel bars forming the grate. Each bar is adjustable along the width of the frame. Pins protruding from beneath the bar drop into a slot in the frame. Spacing between the bars is adjusted by sliding the bars along the slot. Once the desired spacing is obtained, tension wedge locks are placed through openings in the pins to secure the bars to the frame. Spacing along the frame can be further controlled by matching spot faces on the bars to evenly spaced buttons positioned along the frame. Engaging the spot faces and buttons prevents lateral movement of the bars while the grizzly is in use. Total adjustability along the width of the frame allows a single grizzly to be used to sort rock for crushing from gravel which is to be used as road base, or to size gravel for use as top dressing.